Conflicts between the SIP ALG and the session helper

Conflicts between the SIP ALG and the session helper

If you suspect that the SIP session helper is being used instead of the ALG, you can use the diagnose sys sip command to determine if the SIP session helper is processing SIP sessions. For example, the following command displays the overall status of the SIP sessions being processed by the SIP session helper:

The diagnose sys sip command only displays current status information. To see activity the SIP session helper has to actually be processing SIP sessions when you enter the command. For example, if the SIP session helper had been used for processing calls that ended 5 minutes ago, the command output would show no SIP session helper activity.

This command output shows that the session helper is not processing SIP sessions because all of the used and count fields are 0. If any of these fields contains non-zero values then the SIP session helper may be processing SIP sessions.

Also, you can check to see if some ALG-only features are not being applied to all SIP sessions. For example, FortiView pages displays statistics for SIP and SCCP calls processed by the ALG but not for calls processed by the session helper. So if you see fewer calls than expected the session helper may be processing some of them.

Finally, you can check the policy usage and session information dashboard widgets to see if SIP sessions are being accepted by the wrong security policies.

Michael Pruett, CISSP has a wide range of cyber-security and network engineering expertise. The plethora of vendors that resell hardware but have zero engineering knowledge resulting in the wrong hardware or configuration being deployed is a major pet peeve of Michael's. This site was started in an effort to spread information while providing the option of quality consulting services at a much lower price than Fortinet Professional Services.